This invention relates in general to a transfer assembly for use for example in a reproduction apparatus, and more specifically to a mounting mechanism for a roller transfer assembly accurately positioning the roller transfer assembly in operative relation with a dielectric member of a reproduction apparatus.
In reproduction apparatus, such as copier/duplicators or printers, a latent image charge pattern is formed on a uniformly charged dielectric member. Pigmented marking particles are attracted to the latent image charge pattern to develop such image on the dielectric member. The dielectric member is then brought into contact with a receiver member, and an electric field is applied to transfer the marking particle developed image to the receiver member from the dielectric member. After transfer, the receiver member bearing the transferred image is transported away from the dielectric member and the image is fixed to the receiver member by heat and/or pressure to form a permanent reproduction thereon.
Application of the electric field to effect marking particle transfer is generally accomplished by ion emission from a corona charger onto the receiver member while in contact with the dielectric member, or by an electrically biased roller urging the receiver member against the dielectric member. Roller transfer apparatus offer certain advantages over corona transfer apparatus in that the roller transfer apparatus substantially eliminate defects in the transferred image due to paper cockle or marking particle flakes. This result stems from the fact that the pressure of the roller urging the receiver member against the dielectric member is remarkably efficient in providing intimate uniform contact therebetween. However, roller transfer apparatus are more complex than corona transfer apparatus in that they require cleaning due to their tendency to pick up marking particles from the dielectric member and undesirably deposit such particles on the back side of the receiver member. Further, the roller transfer apparatus, including the cleaning assemblies must be constructed so as not to interfere with ready clearance of any jammed receiver members. An example of a selectively positionable roller transfer apparatus constructed to include a cleaning mechanism is shown in U.S. Pat. No. 5,101,238 (issued Mar. 31, 1992, in the names of Creveling, et al).
While roller transfer apparatus are generally effective in carrying out desired marking particle image transfer, they tends to impose undesirable tracking effects on the dielectric member, particularly when the dielectric member is in the form of an elongated web. U.S. Pat. No. 5,491,544 (issued Feb. 13, 1996, in the names of Kenin et al) shows a transfer assembly, of compact configuration, for a reproduction apparatus. The transfer assembly includes a transfer roller for effecting transfer of a pigmented marking particle image from an elongated web dielectric member to a receiver member. A mechanism for mounting the roller transfer assembly includes a support for the transfer assembly connected to the transfer assembly such that the transfer roller of the transfer assembly is castered and gimbaled. However, this mechanism relies on the weight of the transfer assembly to establish the proper engagement with an unsupported span of the dielectric member. Since the weight of the transfer assembly cannot be controlled within tight enough tolerance limits, the described mechanism does not position the transfer roller with sufficient accuracy.